This invention relates to the technology of magnetic circuits for electronic devices, particularly to the adaptation and utilization of permanent magnets rather than electromagnets in applications for such devices and, more particularly, to the use of rare earth permanent magnet materials in the construction of apparatus for the production of axially extending electromagnetic fields and for the precise control and leakage-free containment thereof.
The utilization of permanent magnet devices and structures of permanent magnets to replace electromagnetic type yokes in electronic devices, cathode ray tubes for instance, has received significant acceptance in the electronics industry. To achieve the proper operation of electron beam type devices it is most times necessary to apply a magnetic field having its flux lines parallel to the longitudinal axis of the travel path of the electrons being controlled. Conventionally, this space of electron travel assumes the shape of an elongate cylinder, and the flux lines to be developed parallel to the axis of such cylinder have been traditionally produced for many years by shielded solenoids. Such solenoids require extremely critical power regulation, and if the field strength is of a significant magnitude, cooling may be required. The power and cooling requirements of such electromagnetic and solenoid devices have been advantageously replaced by the present day developments in the use of permanent magnet structures to produce the longitudinally extending linear flux fields for the control of these electron beam streams. More recent advances in the art have found advantage in the application of the rare earth permanent magnet materials and, generally, permanent magnet materials characterized by having a square hysteresis feature.
Various prior art devices have contributed to the development of the technology in this area. The U.S. Pat. No. 3,768,054, for example, to Neugebauer, entitled "Low Flux Leakage Magnetic Construction", teaches a number of magnetic circuits and devices which utilize magnetic cladding means to reduce or contain the interior flux leakage and increase the controlled magnetic field intensity. The advantageous features of this and similar devices are, significantly, the reduction of flux loss and very effective control without any increase, in fact most times a decrease, in the size and weight of the magnetic circuit devices and elements.
In my own co-pending application Ser. No. 685,426, filed Dec. 24, 1984, entitled "Lightweight Cladding for Magnetic Circuits", I disclose and claim the advantageous features of certain magnetic structures arranged with flux fields transverse to each other and with tapered thicknesses of the restraining or cladding magnet elements in order effectively to control and maintain the linearity and constancy of the working flux in the flux spaces interior of such devices. In another co-pending application, application Ser. No. 861,464, filed May 1, 1986, and entitled "Confinement of Longitudinal Axially Symmetric Magnetic Fields to Annular Regions With Permanent Magnets", I describe and claim my invention relating to the provision of a device which produces a magnetic field, annular in shape using the basic design concept of arranging cladding magnets with flux directions transverse to the main supply magnet flux directions.
With the attainment of greater advances in the art the desideratum of further miniaturization of such devices has arisen. It is readily apparent that with steps taken towards the reduction of weight and size of the various magnetic elements comprised in these rare earth permanent magnet structures, the limits of miniaturization have not yet been fully developed or explored. Prior to the time of the present invention, the cladding magnet elements in the various structures described and referred to hereinabove have been made by shaping and forming cladding magnet elements and parts with the flux fields arranged in the desired transverse direction, and then applying or attaching these to the basic magnetic structure, whether it be concentric sleeves or simple cylindrical or square type structures. In some recent development work performed by F. J. Cadieu et al, described in the Journal of Applied Physics, 55-6, page 2611, 1984, and in further treatment of this area of the technology by F. J. Cadieu et al in later papers presented in August 1985, the concept of depositing relatively high energy product of rare earth permanent magnet material such as 18-21 MGO.sub.e and/or SmCo.sub.5 type films onto various substrates, afforded an opportunity for the concept and development of my invention according to this application. Cadieu's work involved the formation of a magnetic device of film or strip form by the deposition method known as "Sputtering", and then forming a flux field or working space within such laid down film or strip by drilling a hole or a tunnel therethrough just beneath the deposited material. Of particular interest is the fact that the Cadieu type films laid down according to the sputtering technique can be deposited with orientations either parallel to or normal to the planes of their substrates.
With this then being the state of the art, I conceived and developed the present invention to provide for the control of linearly extending flux fields in very small magnetic devices utilizing permanent magnet structures.
It is a primary object of the present invention to provide a method and apparatus for permanent magnet structures made from rare earth materials and wherein magnetic flux fields can be controlled with great precision in very small physical environments substantially without the occurrence of flux leakage.
It is a further object of this invention to provide apparatus and method for the control of axially extending longitudinal magnetic flux fields, including particularly the containment thereof, by the application of varying or tapered thicknesses of permanent magnet depositions arranged and disposed along the length of the supply magnets of such devices and with the deposition material flux oriented transverse to the flux of the magnetic element which produces the axially extending field.
A still further object of the invention is to provide permanent magnet structures and a method for making them which involves the deposition of high energy rare earth magnetic field products in tapering thicknesses along the longitudinal dimension of basic magnetic elements within which axially extending magnetic flux fields exists.
It is a further and particular object of this invention to provide for the fabrication of extremely, heretofor unattainable, miniaturized permanent magnet structures by the technique of deposition of a magnetic layer of axial orientation flux on very small dimensioned cylindrical core thicknesses, in the order of the thickness of a human hair and the like, and, by means of the precise control of radially oriented flux layers deposition, obtain the control of magnetic fields in the order of a few thousand oersteds.